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Laguna Beach Reunion: Lauren Conrad's Book Launch Attracts Some Familiar MTV Faces

The LBHS students are still celebrating (pun intended) important milestones.

Lauren Conrad has always had the support of her hometown Laguna Beach buddies at milestone events -- specifically, saying "I do" to William Tell and her New York Fashion Week debut. And now, a few of the lifestyle maven's LBHS 2004 classmates were on hand for a special occasion: celebrating (pun intended) the release of her new party-planning book Celebrate.

"Congrats @laurenconrad on her new incredibly gorgeous and useful book. And a great party to boot!" Trey Phillips captioned the cute Instagram image above, featuring LC as well as Dieter Schmitz at the Big Apple bash. Feels like only yesterday these three were taking photos at prom and tearfully embracing at graduation.

Back to present day: Dieter also shared a snap with his best bud at the Pinterest-perfect event.

"Congrats @laurenconrad for the Celebrate release! @treyphillips and I had a blast," he added along with the photo. Looking FIERCE with those pink streamers, guys!

And, last but not least, the guest of honor also posted a glimpse of the special evening.

"@leslieannebruce and I wrote a book! And tonight we celebrated!!" the Hills alum wrote. Cheers to you, Lauren!

Be sure to get your copy of Celebrate next week (March 29, to be exact) -- and because it's Throwback Thursday, watch the MTV trio at their prom in the old-school clip below!